The present disclosure generally relates to polymers that are useful in papermaking processes. More particularly, the present disclosure relates to polyamine-polyamidoamine-epihalohydrin compositions, methods of manufacture, and their use.
The creping application generally includes scraping a dried paper web from a drying cylinder (e.g., a Yankee dryer) by the use of a creping doctor blade. The creping action puts very small folds or accordions in the sheet to impart a fine, rippled texture to the sheet, which also increases the bulk, softness and absorbency of the sheet. Creping can occur when the sheet is almost completely dry, that is, 92 to 98% solids or when the sheet is wetter, around 70-85% solids. If the machine is designed to crepe at high dryness, it is referred to as a “dry crepe” machine. Dry creping has the greatest effect on sheet properties because the sheet is more firmly attached to the Yankee surface. If the machine is designed to crepe when the sheet is still somewhat wet, it is called a “wet crepe” machine.
Adhesion of the sheet to the drying cylinder is an important aspect of the creping process since it determines how the sheet crepes at the doctor blade. Sheet adhesion is generally controlled through application of an adhesive formulation onto the Yankee dryer surface. The creping process typically involves applying the creping adhesive, generally in the form of an aqueous solution or dispersion, to a drying surface for the web. Typically, this surface is the surface of a rotating heated creping cylinder, such as the Yankee dryer discussed above. The paper web is then adhered to the indicated surface and later dislodged from the surface with a creping device, e.g., using a doctor blade. The impact of the web against the creping device ruptures some of the fiber-to-fiber bonds within the web, causing the web to wrinkle or pucker. In this regard, fibrous webs, particularly paper webs, are conventionally subjected to the creping process in order to give them desirable textual characteristics, such as softness and bulk. It is well known that the use of adhesive formulations can provide improved product quality and better control of the papermaking process.
Drying cylinders such as the Yankee dryer are often operated under quite different temperature conditions, ranging from 90° C. to 130° C. Recent trends have the creping conditions moving towards high temperature and/or low sheet moisture. Under high temperature conditions, “rewettability” of the applied adhesive is critical to impart the adhesion of the sheet to the Yankee dryer. Rewettability refers to the ability of a dry adhesive film on the dryer to absorb water once in contact with the wet paper sheet. The adhesive is typically sprayed on the Yankee coating continuously. However, the majority of the adhesion occurs by means of the adhesive deposited in previous passes. If the adhesive absorbs greater amounts of water in contact with the sheet, the adhesive will be softer, resulting in a more intimate contact with the sheet and providing increased adhesion between the sheet and the dryer.
The solubility of the adhesive film in water is another essential property affecting adhesion. The wet sheet before the Yankee dryer typically contains
60% or more water. During the contact between the wet sheet and the Yankee dryer, water from the sheet may wash off a portion of the deposited adhesive coating, negatively impacting the efficiency of the creping process. In order to form a durable enough coating on the Yankee surface, relatively low water solubility (high insolubility) is often required for the adhesive film to withstand the wash-off at the point of contact with the wet sheet.
Polyamidoamine epichlorohydrin resins (PAE resins) have been applied in the manufacture of paper for a variety of applications. For example, PAE resins are widely used as strength additives to increase the paper wet strength. PAE resins are also the most common adhesives used in the creping process for producing tissue and towel products.
Conventional PAE resins are typically produced in a two step reaction. In the first step, a polyamidoamine is prepared by condensation of near equi-molar amounts of a polyamine and a polycarboxylic acid or polycarboxylic acid derivative. The polyamidoamine that is formed is then reacted with epichlorohydrin in an aqueous solution to produce the PAE resin. The detailed synthesis is well known and is documented in numerous patents, e.g., U.S. Pat. Nos., 2,926,116, and 7,175,740.
Much research has been carried out to develop modified PAE resins with improved performance for various applications. U.S. Pat. No. 3,951,921 describes a cationic water soluble resin consisting essentially of a PAE base resin having epoxide moieties and a nitrogen compound in an amount at least stoichiometrically equivalent to the epoxide moieties of the base resin. The nitrogen compounds are ammonia, ethyl amine, dimethyl amine and hydroxylamine U.S. Pat. No. 4,287,110 describes a PAE resin made form a polyamidoamine and an excess polyamine wherein the molar ratio of dicarboxylic acid to polyamine is 1:1 to 1:2. U.S. Pat. No. 5,338,807 is generally directed to a creping aid composition including a polyamide reaction product of an polyamide of a polycarbonxylic acid or of the ester of an aliphatic dicarboxylic acid and methyl bis(3-aminopropyl)amine with epichlorohydrin in a mole ratio of the polyamide to the epichlorohydrin between about 1:0.1 and about 1:0.33. U.S. Pat. No. 5,382,323 is generally directed to a creping aid of a polyamidoamine crosslinked with a multifunctional aldehyde. US Pat. Pub. No. 2008/0255320 is generally directed to a PAE resin made from a polyamidoamine with an excess polyamine, wherein the molar ratio of polyamine to polycarboxylic acid is in the range of 1.02:1 to 2:0.1.
While these PAE adhesive formulations are adequate for many creping applications, there is a continuing need for an adhesive with improved properties, including film rewettability, film insolubility, and adhesion.